Plasticizer from polymethylol alkanes and 3-alkyl alkanoic acids and polymeric compositions containing same



PLASTICI ZER FROM POLYMETHYLOL ALKANES AND 3-ALKYL ALKANOIC ACIDSANDPOLY- MERIC COMPOSITIONS CONTAINING SAlVIE Fred W. Banes and IsidorKirshenbaum, Westfield, and Jeffrey H. Bartlett, New Providence, N.J.,assignors to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Application June 6, 1957 Serial No. 663,883

16 Claims. (Cl. 260-316) The present invention relates to plasticizersand particularly to the use of certain esters a's plasticizers in theformulation of synthetic resins. Specifically, it relates to superiorplasticizers made by the esterification of di-, tri-, or tetramethylolalkanes containing a neopentyl carbon atom solely with certain specificbranched-chain acids,

viz., 3-alkyl alkanoic acids, having from 6 to 9 carbon atoms.

This application is a continuation-in-part of co-pending applicationSerial No. 607,564, filed September 4, 1956.

In the earlier case it was noted that esters of trimethylol alkanesproduced from (I -C acids, when cornbined with synthetic resins such asthose prepared from vinyl compounds, give a product having agingcharacteristics superior to those obtained with conventionalplasticizers such as di-isooctyl phthalate (DIOP) and di-Z- ethyl hexylphthalate (DOP). Contrary to earlier teachings that straight-chain acidesters are better plasticizers than branched-chain acid esters, it wasfound that mixtures of 'straightand branched-chain acids also producepresent plasticizers result 'in improved plasticizer efficiency asevidenced by torsional modulus and as evidenced by tensile andelongation retention.

Therefore, an object of the present invention is to prepare a. novelester plasticizer from a polymethylol alkane and a pure branched-chainacid. Another object is to provide an efiicient plasticizer for theformulation of stable resinous polymers. A further object is to providea convenient and economic method of preparing a plasticizer for resinouspolymers.

The branched-chain acids suitable for the invention are the 3-alkylalkanoic acids having from 6 to 9 carbon atoms, i.e., 3-methylpent-anoic acid, 3-methyl hexanoic acid, 3-methyl heptanoic acid,3-'ethyl pentanoic acid, 3-ethyl hexanoic acid, 3-methyl octan'oic acid,etc., or mixtures thereof. The 3-methyl hexanoic acid is preferred, andit may conveniently be prepared in a'highly pure'form by. thedimerization of propylene to form 2- methyl pentene-l (according to themethod of Ziegler as described in US. Patent 2,695,327) and thesubsequent oxonation of the dimer olefin to the 3-methyl hexanoic acid.Correspondingly, the other above-mentioned acids can be prepared by asimilar combination of dimerization and oxonation steps. However, thisinvention 'is not limited to any particular source of the acids, thesole requirement being that the acid is obtained in a relatively purestate, i.e., at least 80% pure.

The polymethylol alkanes which may be used are the Patented Jan. 5, 1960di-, tri-, and tetrarnethylol alkanes having a total of 5 to 11 carbonatoms and wherein the methylol groups are attached to the same neopentylcarbon atom. Accordingly, these polymethylol's may formula: CHzOHY-dI-CH:OH

. Y' wherein Y and Y are selected from the group consisting of 'CH OHand C -C alkane groups and where the carbon atoms in Y-l-Y' do not totalmore than 8. Included within this definition are p'entaerytl'iritol,'trimethylolethane, trimethylolp'ropane', trimethylol-n-butane,"trimethylolisobutan'e, trimethylolpentane, trimethylolhex'ane,trimethylolheptane, trimethyloloctane, 'neopentyl glycol, etc. The C -Ctrim'e'thylol's and pentaerythritol are preferred. The polymethylolderivatives are generally prepared from the corresponding aldehyde,i.e., aldehydes having one or more active hydrogen atoms attached 'tothe carbon atom adjacent to the"aldehy'de group. For example,pentaerythri'tol is'prep'a'red by 'the reaction of acetaldehyde withformaldehyde -in the presence of a basic catalyst; trimethylolbutanefrom n-valeric aldehyde and formaldehydeydime'thyl neopentyl glycol fromisobutry'aldehyde and formaldehyde, etc. 'Any source of aldehyde, ofcourse, is suitable such as those prepared by the "0x0 synthesis,involving the reaction of an olefin'with carbon 'monoxide andhydrogen inthe presence of a cobaltcontainingfcatalyst.

In the preparation ofbthe trimethylol esters, approximatelyl to 2 moles,preferably about 1.1 to 1.2 moles, of the 3-a1kyl alkanoic acid isreacted with each mole of available hydroxyl group 'of the polymethylolalkane. The reaction is conducted in the presence of a waterentrainingagent such as toluene, xylene, heptane, or other suitable hydrocarbonsor the like, and about 0.5 to 5.0 weight percent of an esterificationcatalyst such as sulfuric acid, para-toluene sulfonic acid, etc., permole of polymethylol. The esterification generally takes between 2 and10 hours at a temperature between 100 and 200 C., preferably 3 to-5;hours at-125 to 175 C.

When the 3'-alkyl alkan'oicacid is prepared by the preferred; methodof'dimerization. according to the process described in US. :Patent2,695,327, followed by OXonation of the-resulting; dimernthe conditionsare as follows. The dimerization is carried out at temperatures rangingfrom 80 to 250 C., inthe presence of a dimerization activator such asaluminum tripropyl, aluminum 'tiihydride, other aluminum trialkyls, andequivalents. The reaction pressure is maintained between'atmosphe'ricand 30,000 p.s.i.g. or greater. The 'oxonation of the dimer isconductedatpressures between 1,000and 6,000 p.s.i.g.

. :and at temperatures between 70 and 200 C. The rev sultingaldehydeis-oxidized by airor oxygen blowing at atmospheric pressure and attemperatures between 20 and 100 C., preferably between 40 and 50 C. Theacid is thenpurified by fractional. distillation or similar means and isrecovered in at least purity, preferably 98-99% purity.

When the polymethylol alkanes are prepared by the Oxo synthesis of thealdehyde followed by the conversion of the aldehyde to the polymethylol,the conditions are as follows. The oxonation reaction is conducted inthe same manner and under the same temperature and pressure asdescribedabove-with reference to the alkanoic acid preparation. TheOxoaldehyde, or any aldehyde, is then reacted with formaldehyde in thepresence of a caustic, preferably between 10 and 15 C., for the firsthalf of the reaction. The temperature is then raised above roomtemperature, preferably between 50 and 60 C. for the second half of thereaction, whereupon the reaction mixbe represented by the atmospheres.

ture is neutralized and the aqueous phase is separated from the organicpolymethylol alkane phase.

In the practice of the present invention, the 3alkyl 'alkanoic acidesters of the polymethylol alkanes are effi- ,to use between about 40and 60. parts by weight of plasticizer.

For instance, in the case of resins prepared with vinyl chloride, asatisfactory formula may contain about 50 parts by weight of theplasticizer.

The polymers in which the plasticizers of. the present invention areparticularly effective are synthetic resins prepared from vinylcompounds, such as vinyl chloride, vinyl acetate and copolymers thereof,as well as from vinylidene chloride, acrylates, and the like. acetatecopolymers are preferable and are generally composed of about 80 to 95weight percent vinyl chloride and 5 to 20 weight percent vinyl acetate.The polymerization is usually carried out between about 20 and 100 C. inthe presence of a peroxidecatalyst, such as benzoyl peroxide, acetylbenzoyl peroxide, etc. The specific viscosity (68/68 F.) of these resinsis generally between about 0.2 to 1.2.

In addition to the plasticizer, the resin may contain various knownstabilizers. Suitable as stabilizers are substituted phenols such asp-ethoxyphenol, pand m-aminophenol, diethyl ether of hydroquinone, etc.;amines such as 2-nitrodiphenylamine, 2-ethyl hexylamine, etc.; ureaderivatives such as phenyl thiourea, diphenyl guanidine, etc.; azolinecompounds such as 2-imidazoline-2-thiol, 5,5-dimethyl-2-mercaptooxazoline, etc.; azole compounds such asZ-mercaptothiazole, 2-mercaptobenzoxazole, etc.; heavy metal-containingorganic compounds such as barium ricinoleate, dibasic lead stearate,dibasic lead carbonate, cadmium naphthenate, strontium and zinc laurate,dibutyl tin dilaurate, etc.; organo phosphorus compounds such astriphenyl phosphite, trioctyl phosphite, sodium organophosphate, e.g.,Vanstay, and the like. These substances are generally used in amountsbetween about 0.1 and 15 parts by weight per 100 parts by weight ofpolymer, but it is preferred to use between about 1 to 5 parts by weightof stabilizer. In addition, cadmium and calcium stearate can be used aslubricants as well as stabilizers. Phenyl salicylate, resorcinoldibenzoate and phosphates and the like may be used to stabilize theresin against discoloration in sunlight.

The following specific examples are submitted in order to give a betterunderstanding of the present invention, but not to limit the invention.Unless otherwise specified, all ratios and percentages are giventhroughout on a weight basis.

EXAMPLE I (A) Preparation of 3-methyl hexanoic acid Thirty moles ofliquid propylene was mixed in an autoclave and heated with one mole ofaluminum tripropyl (diluted to a volume percent solution in pentane) toa temperature of about 180 C. and a pressure of about 170 After a fewhours, the pressure dropped to about 40 atmospheres and additionalpropylene was added under pressure. The reaction was continued until theautoclave was filled with reaction products, and propylene at constantvolume temperatures between about 150 and 180 C. and at a pressure ofabout 3,500 p.s.i.g., in the The .vinyl chloride presence of a cobaltcarbonyl catalyst preformed from cobalt acetate (0.1% Co based on dimerfeed) and a 1/1 ratio of CO and H After 5 hours the crude reactionproduct was decobalted by washing with an aqueous solution of cobaltacetate, water-washing, and distilling. The purified 3-methylhexanal-1was then air blown at about 40 to 50 C. and the product was fractionallydistilled. Three-methyl hexanoic acid was recovered in 98-99% purity.

(B) Preparation of trimethylolisobutane Isobutylene was oxonated in thesame manner as the propylene dimer in A, at a temperature between 150and 180 C. and a pressure of about 3,500 p.s.i.g. One mole of resultingisovaleraldehyde, 4 moles of formaldehyde in a 37% aqueous solution, and1 mole isopropyl alcohol were charged to an open reactor. One andone-tenth moles of sodium hydroxide cc. in aqueous solution) were slowlyadded to the other reactants with vigorous stirring, maintaining thetemperature between 10 and 15 C(for 3 hours. The temperature was thenraised and maintained between 50 and 60 C. for another 3 hours. Thereaction mixture was neutralized and an aqueous phase separated from anorganic phase. The aqueous layer was salted out with NaCl and extractedwith isopropyl alcohol. The alcohol extract was added to the organiclayer and the isopropyl alcohol was then evaporated on a steam bath. Theremaining crude trimethylolisobutane was extracted with acetone,filtered, and distilled. The resulting pure product distilled at C. atabout 0.5 mm. pressure. It was a white solid melting at82 C.

(C) Preparation of ester of trimethylolisobutane and 3-methyl hexanoicacid One mole (148 gms.) of the alcohol product of B and 3.3 moles (429gms.) of the acid product of A in the presence of 2 gms. of p-toluenesulfonic acid were mixed with 300 cc. of toluene and the solutionmaintained at the boiling point of the mixture until no more water couldbe removed as an azeotrope. The reaction mixture was then diluted withtoluene and. washed with 5% NaOI-I solution and finally with water toremove all acids. Toluene was evaporated on a steam bath and the crudeester was purified by vacuum distilling through a short path still.

EXAMPLE II In this example, polymers were compounded according to thefollowing formula in which the only variable is the particularplasticizer under consideration:

Geon 101 is a 100% polyvinyl chloride resin. It is a white powder havinga specific gravity of 1.40:0.05, a specific viscosity of 0.52 to 0.57, aheat loss maximum of 0.5% and an ash of 0.4%. One hundred parts byweight of the polyvinyl chloride resin was admixed with 1 part dibasiclead stearate to form a dry blend. Next, 50 parts by weight ofplasticizer were mixed with the blend until an almost lump-freecomposition was obtained. The resulting mixture was then homogenized ina Banbury mixer,land sheeted into a 'finished film having a thickness ofbetween about 0.075 and 0.15 inch.

Polymer compositions were prepared according to the above recipeemploying a branched-chain polymethylol plasticizer of the presentinvention as well as conventional DIOP and DO? plasticizers,straight-chain polymethylol ester plasticizers, and branched-chaintrimethylol esters of acids-other than 3-alkyl alkanoic acid. Thephysical properties of the finished product were determined on theaforedcscribed ,molded films, and the aging characteristics weredetermined after heating the films in an air oven, conventionallydesigned for temperature and air circulation, at a temperature of about100 C. for a period of 7 days. All these properties are tabulated inTable I.

The value of a plasticizer is measured by the tensile strength of thepolymer plasticized, the 'percentageelongation of the polymer, thepercentage of these original properties retained after aging of thepolymer, and the torsional modulus of thepolymer at room and lowtemperatures. The higher the tensile strength, the percentageelongation, and the percentage retention, and the lower the modulus, thebetter is the plasticized polymer. The data in Table I are strongevidence of the superiority of the polymethylol esters of alkanoic acidshaving an alkyl group at the 3 position on the alkanoic chain. There itis observed that the plasticizer of the instant invention (run 1)results in polymers of much better low temperature modulus and agingcharacteristics than the conventional DIOP (run 2) and DOP (run 3)plasticizers. The instant plasticizer is superior to straight-chain acidesters (runs 4 and 5) with respect to original tensile and elongationproperties. In addition, the branched-chain acid from which the presentplasticizer is made is more readily obtained than the straight-chainacids. Finally, it is noted that other branched-chain acid esters (run6) are highly inefiicient, especially with respect to agingcharacteristics and low temperature modulus. The C OX0 acid of run 6 isa mixture of various branched-chain acids, especially rich in 2-methylhexanoic acid and other acids not substituted at the 3 position,produced via the 0x0 reaction. For the advantages of the presentinvention to be fully realized, the alkyl group must be substituted atthe 3 position of the alkanoic acid. The 3-alkyl alkanoic acid must beobtained in a relatively pure form, i.e., 80%, in order to keep otherbranched-chain acids from inhibiting its especial value.

B actant having '6 'to 9. carbon atoms to the molecule, said reactantbeing at least 80% 3-alkyl alkanoic acids, and a C 0 'triinethylolalkane reactant wherein the methylol groups are attached to the sameneopentyl carbon atom, said reactants being reacted at a temperaturebetween 100 and-200 C. I v

4. Aplasticize'r according to claim 3 wherein 1 to 2 moles of the acidreactant are reacted per mole of available hydroxyl group on thetrimethylol alkane reactant.

5. A plasticizer according to claim 3 wherein the 3- alkyl alkanoicacids are 3-methyl hexanoic acid.

6. A plasticizer according to claim 3 wherein the trimethylol alkane istrimethylolisobutane.

7. A plasticized polymeric composition which comprises 100 parts byweight of a polyvinyl resin selected from the group consisting ofpolyvinyl chloride, polyvinyl acetate and vinyl chloride-vinyl acetatecopolymers and to 75 parts by weight of the ester of a 3-alkyl alkanoicacid having 6 to 9 carbon atoms and a polymethylol alkane selected fromthe group consisting of di-, tri-, and tetramethylol alkanes having atotal of 5 to 11 carbon atoms and wherein the methylol groups areattached to the same neopentyl carbon atom.

8. A plasticized polymeric composition according to claim 7 wherein saidpolyvinyl resin is polyvinyl chloride.

9. A plasticized polymeric composition according to claim 7 wherein saidpolyvinyl resin is polyvinyl acetate.

10. A plasticized polymeric composition according to claim 7 whereinsaid polyvinyl resin is a copolymer of 80 to 95 weight percent vinylchloride and 5 to 20 weight percent vinyl acetate.

11. A plasticized polymeric composition which comprises 100 parts byweight of a polyvinyl resin selected from the group consisting ofpolyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetatecopolymers; 25 to 75 parts by weight of the ester of a C C alkanoicacid,

TAB LE I Original Physical Properties Aging Characteristics RunPlasticizer Torsional Modulus Tensile Elongation Tensile Elonga-Strength Retained, Strength, tion, Retained, Percent of p.s.i.g. Percent+25 C. 25 C. Percent of Original Original Ester of trimethylolisobutaneand S-methyl 2, 900 320 0. 37 15 100 97 hexanoic acid. DIOP 3, 000 3050. 34 24. s DOP 3, 000 315 0. 34 27. 3 90 62 Ester;1 oftrimethylolisobutane and n-heptanoic 2, 775 295 0. 16 3 96 98 amEStQILIOi trimethylolisobutane and n-octanoic 2, 570 275 0. 48 14.8 102104 am Ester of trimethylolisobutane and 0 0x0 acid 2, 885 310 O. 33 27.9 87 69 prepared from mixed C olefins.

Having described the general nature and use of the present invention,the true scope is particularly pointed out in the appended claims.

What is claimed is:

l. A plasticizer for synthetic resins comprising the ester of a 3-alkylalkanoic acid having a total of 6 to 9 carbon atoms and a polymethylolalkane selected from the group consisting of di-, tri-, andtetramethylol alkanes having a total of 5 to 11 carbon atoms and whereinthe methylol groups are attached to the same neopentyl carbon atom.

2. A plasticizer according to claim 1 wherein the polymethylol alkane isa trimethylol alkane having 6 to 8 carbon atoms, and the alkanoic acidis 3-methyl hexanoic acid.

3. A plasticizer for synthetic resins consisting essentially of theesterification product of an alkanoic acid resaid acid being at least3-alkyl alkanoic acid, and a C -C trimethylol alkane wherein themethylol groups are attached to the same neopentyl carbon atom; and 0.1to 15 parts by weight of an organic stabilizer for said polyvinyl resin.

12. A plasticized polymer according to claim 11 wherein the trimethylolalkane is trimethylolpropane.

13. A plasticized polymer according to claim 11 wherein the trimethylolalkane is trimethylolisobutane.

14. A plasticized polymer according to claim 11 wherein the trimethylolalkane is trimethylol-n-butane.

15. A plasticizer for synthetic resins consisting essentially of theesterification product of an alkanoic acid reactant having 6 to 9 carbonatoms to the molecule, said reactant being at least 80% 3alkyl alkanoicacid, and pentaerythritol reactant, said reactants being reacted at atemperature of between and 200 C.

16. A plasticized polymeric composition which c0mprises 100 parts byweight of a polyvinyl resin selected from the group consisting ofpolyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetatecopolymers; 25 to 75 parts by Weight of the ester of a C -C alkanoicacid, said acid being at least 80% 3-alkyl alkanoic acid, andpentaerythritol; and 0.1 to 15 parts by weight of an organic stabilizerfor said polyvinyl resin.

References Cited in the file of this patent UNITED STATES PATENTSDebacher Oct. 15, 1946 Ziegler Nov. 23, 1954 Buckmann Jan. 3, 1956Whitaker Jan. 29, 1957

1. A PLASTIZER FOR SYNTHETIC RESINS COMPRISING THE ESTER OF A 3-ALKYLALKANOIC ACID HAVING A TOTAL OF 6 TO 9 CARBON ATOMS AND A POLYMETHYLOLALKANE SELECTED FROM THE GROUP CONSISTING OF DI-, TRI-, ANDTETRAMETHYLOL ALKANES HAVING A TOTAL OF 5 TO 11 CARBON ATOMS AND WHEREINTHE METHYLOL GROUPS ARE ATTACHED TO THE SAME NEOPENTYL CARBON ATOM.